1. Field of the Invention
The present invention relates to a rotary cylinder device for controlling operations of a chuck to be used on a lathe or the like.
2. Description of the Related Art
Generally, a rotary cylinder device is constructed by fitting a piston axially sidably in a cylinder unit, supporting the cylinder unit for rotation in a bearing on a distributor, and fitting the distributor in an annular draining space formed in a housing. A rotary cylinder device disclosed in JP-B-63-41689 (reference 1) has a distributor positioned and held fixedly in place in an annular space with a bolt screwed in a housing so that its tip is pressed against the distributor. Another rotary cylinder device disclosed in JP-A-61-241505 (reference 2) has a distributor held fixedly in place in an annular space with a bolt screwed in a housing so that its free end part is fitted in a radial hole formed in the distributor.
Vibrations may be generated in those prior art rotary cylinder devices if the distributor makes a slight turning movement in a direction opposite to a direction in which the cylinder unit rotates at a high rotational speed. Therefore, the distributor is fastened to the housing with the bolt as mentioned in the references 1 and 2. In the reference 1, the bolt is pressed against a part of the distributor separated from an annular groove, such as an oil passage, formed in the distributor and hence the bolt is pressed unavoidably against a part of the distributor near the bearing. Consequently, it is possible that the bearing is distorted by pressure exerted on the distributor by the bolt. In the reference 2, if foreign matters are caught in the thin annular space between the distributor and the cylinder unit and cause seizure between the distributor and the cylinder unit, the distributor is forced to rotate together with the cylinder unit. Therefore, it is possible that the torque of the cylinder unit is transmitted through the distributor and the bolt to the housing and the housing is forced to rotate together with a high-pressure hose connected thereto.
Seizure between the cylinder unit and the distributor can be known from the excessive rise of load on the spindle motor of a lathe or the like. However, the excessive load that may be produced by seizure between the cylinder unit and the distributor and may be exerted on the spindle motor must be greater than a load corresponding to a cutting force necessary for machining. Therefore, the rotary cylinder device may be damaged seriously and troubles will occur before seizure between the cylinder unit and the distributor is detected.